Vinyl asbestos formulations particularly those used in vinyl asbestos tiles are generally composed of polyvinyl chloride or polyvinyl chloride-polyvinyl acetate polymers, a plasticizer, a plasticizer stabilizer, a hydrocarbon resin, asbestos, fillers such as calcium carbonate, pigment and colorants such as titanium dioxide, and lubricants and heat stabilizers. A commonly employed heat stabilizer is melamine. It has been found that when certain types of asbestos are used in combination with the melamine in the formulation, there is produced a pink discoloration in the finished tile. These vinyl asbestos tiles, therefore, are subject to discoloration.
In the prior art, the patentees of U.S. Pat. No. 3,314,906 claim the use of rosin acids to avoid the pink discoloration problem. However, it has been found that the use of these rosin acids unfortunately require high concentrations and are not effective in many cases and hence their use is a disadvantage. U.S. Pat. No. 3,084,135 discloses and claims a vinyl asbestos composition containing a heat stabilizing amount of melamine; it is noted that when such a formulation also employs certain types of asbestos that the finally produced tile has a pink color. The need for effectively eliminating pink discoloration in finished tiles employing the above-described formulation is of importance.